MIT Unveils Portable, Solar-Powered Water Desalination System 117
An anonymous reader writes "A team from the Massachusetts Institute of Technology's Field and Space Robotic Laboratory has designed a new solar-powered water desalination system to provide drinking water to disaster zones and disadvantaged parts of the planet. Desalination systems often require a lot of energy and a large infrastructure to support them, but MIT's compact system is able to cope due to its ingenious design. The system's photovoltaic panel is able to generate power for the pump, which in turn pushes undrinkable seawater through a permeable membrane. MIT's prototype can reportedly produce 80 gallons of drinking water per day, depending on weather conditions."
80 US gallons (Score:5, Interesting)
Thats 300 liters. Maybe enough for ten people if you are careful. Or a hundred people if you only need drinking water to keep them alive.
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the group built a small prototype [...] the prototype is capable of producing 80 gallons of water a day [...] They estimate that a larger version of the unit, which would cost about $8,000 to construct, could provide about 1,000 gallons of water per day.
So based on your metric this supplies drinking water for over 1000 people. Still need a lot of these for bigger disasters, but $8/person isn't too bad.
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Think about Haiti in the days after the disaster when clean water was unavailable, the airport was partially inoperable and hopelessly overwhelmed, when airlifting hundreds of thousands of gallons of water (or diesel) was infeasible.
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Many random creeks have contaminated water. Sometimes boiling makes them drinkable, often not.
Re:80 US gallons (Score:4, Funny)
Re:80 US gallons (Score:4, Funny)
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If you've got a creek handy that isn't filled with serious pollutants, human waste, decomposing bodies, and loads of pathogens, then yeah, you're idea of relying on random creeks sounds good.
Oh, and be sure to have some cups for the million or so other people who might also want to have a drink.
Get an account! (Score:2)
The AC who keeps coming up with these "Duh this isn't complicated, all you have to do is $ridiculously_oversimplified_idea_that_wont_really_work" should give himself a name, like BadAnalogyGuy.
Maybe SimpleSolutionGuy or RedGreen.
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Re:80 US gallons (Score:5, Interesting)
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the second i read "permeable membrane" i saw this as throw-away tech.
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Personally I think for large scale disasters it makes a LOT more sense to drop 2 of those and two fuel/generator sets and supply 10x more people with fresh water since every cargo flight counts.
then you just have to keep air dropping or trucking in diesel every couple days as well. I think the point of it being solar is that it doesn't use up fuel resources which will likely also be quite scarce in a situation like this.
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for large scale disasters it makes a LOT more sense to drop 2 of those and two fuel/generator sets and supply 10x more people with fresh water since every cargo flight counts.
That may depend on how close together those people are.
If people are spread across a large area in many small villages, then perhaps many small setups is a more suitable option.
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24 units at 1k gallons each = 24k gallons, for 10k people that's 2 gallons per person, per day.
For yours it's 200k gallons for 50k people, which is 4 gallons per person, per day, or double the water ration.
Going by the same standard you'd be supplying 100k people on the standard system using the MIT kid's standard.
As for 'saline water', if it's like the systems I'm used it, it'll handle salt water and even sewage and spit out safe water, if nasty tasting.
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Thats 300 liters. Maybe enough for ten people if you are careful. Or a hundred people if you only need drinking water to keep them alive.
Wait... are you drinking 8 gallons of water per day? Daily showers are a convenience, not a necessity.
Washing may be vital after a disaster when disease starts to spread.
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I am also thinking about cleaning clothing and cooking equipment, medical needs, hydration in hot climates. Supporting rescue workers doing hard physical work. That sort of stuff.
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That's in addition to all the beer, not instead of it, right?
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You need 30 liters a day? (Score:1, Troll)
My god man, your bladder must be made of steel.
Or are you that alienated from the real world that you think people in disasters zones first priority is a daily long hot shower and flushing toilets?
Yes, we use a LOT of water in the west because... well because we can. When the shit hits the fan, 3-5 liters a day can and must be enough. And that is actually a rather liberal amount. Enough to drink, do some cleaning and cook. No it won't give you a life of comfort but guess what, it isn't. It is disaster rel
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Well you could be right but I was trained to estimate high, deliver low.
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Thats 300 liters. Maybe enough for ten people if you are careful.
You think a person needs to use 30 litres of water per day?
Holy shit. We could solve our water problems by teaching people like you.
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Even Lithuania was using more than twice that in 2003:
http://www.grid.unep.ch/product/publication/freshwater_europe/consumption.php [grid.unep.ch]
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You need to pay more attention to this part :
"The leakage in pipes is very high and is often counted as consumption."
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Try again.
"Leakage is generally high and in many cases 30-50% of the water is lost." Even with that, we have the lowest consumer country using at least as much as what you found to be a enormous amount.
http://www.grid.unep.ch/product/publication/freshwater_europe/images/eurohousehold.jpg [grid.unep.ch]
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Brings to mind bushwalking in a remote part of my state. I stuffed up by not taking enough water containers. The walk out happened to be on a cool day. The walk back was at 40C. Two thirds of the way back I was seriously dehydrating. I walked into a shallow lake and drank because I had to. I didn't consider boiling the water. In the future I will.
Gastric infections in the outback are pretty hellish. I struggled to a camping ground and collapsed near a good water tank. I spent the next two of three days (mem
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Better then none, and that is also by machine, put 10 machines side by side on the ocean floor all lined up with the same tubing, you can fill those tubes up enough that it spills into a container and keeps the water there for the people, sort of like a water tower....
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That is rather good. As this doesn't seem that much bigger then a pool pump.
You can truck it in. and hook it up and you have water for a family or too. The big ones that do a lot more needs a full infrastructure which is hard to deploy.
It is like City Water vs Well water. You have the big plants to give water to a City you have this for water for the individual home, out side the infrastructure.
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> maybe enough for ten people if you are careful.
Or enough for 100 people who wouldn't otherwise have .8 gals of water a day to drink.
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I think they could make these cheaper.
http://www.thefarm.org/charities/i4at/surv/sstill.htm [thefarm.org]
They have no moving parts to break, require no electric.
Add a few reflectors such as aluminum foil and increase
your evaporation rate quite a bit.
Damn you, science jornalism. (Score:5, Insightful)
Pump-fed nanofilters are sort of an old idea at this point. The summary leaves off some critical points like how much it costs and how long the filter lasts.
According to the article, it costs $8000, which is a lot for some things but probably accessible for others. Let's just say it's not going to solve the world's water problem overnight, but it might be handy for relief efforts.
Surfing through to the parent MITnews article [mit.edu], we get a bit more information, but it's still lacking anything about how long the system can operate or what its maintenance costs and requirements are. Does it last a week then you're out most of another $8000? Does it require a lot of technical expertise to maintain? It doesn't say...
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Pump-fed nanofilters are sort of an old idea at this point. The summary leaves off some critical points like how much it costs and how long the filter lasts.
Exactly. The panels and pump are probably going to last several years without significant maintenance, but they will need a steady supply of filters to keep the thing going. They could extend the lifetime of them by running them in reverse for some amount of time to clean them out, but you can't do that indefinitely, and the system isn't usable while being back-flushed.
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Hi, AC. Since 1000 gallons of water comes out to about 4.2 short tons (1000 gallons * 3785 cc per gallon * 1 g per cc of water / 907185 g per short ton), you would actually get about 29 tons in a week. If you want to round more, 4 x 7 is 28. Congratulations, you can mostly do basic unit conversions. What was your point? Filter cost and maintainability are still major unreported issues. Also, that $8000 doesn't count incidentals - getting the water there, personnel, transportation, distribution.
P.S. if you s
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MIT is a big school. You get all sorts of projects, really. You also get the usual fluff coverage in the media which tells you next to nothing about the actual project.
MAKE also has coverage ranging from some pretty serious projects to "The Most Useless Machine" and "PLCs: What the heck are they" so it might not be a great comparison against all research churned out by a major academic institution. It has great stuff and it usually does a good job of catering to its audience, but at the end of the day it's
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Simple is good. Its easy to maintain and easy to teach local people to take over maintenance.
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This is precisely what I was thinking. The water filter is neat but it is NOT solar-powered. It is electrically powered, and it is in this case coupled with a solar system which provides the power to operate it. I was excited because I would like a better, cheaper solar-powered desalinator.
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According to the article, it costs $8000, which is a lot for some things but probably accessible for others. Let's just say it's not going to solve the world's water problem overnight, but it might be handy for relief efforts.
Actually, the 8000$ was the expected cost of a larger 1000 gallon version.
A larger version is also being designed, which will cost $8,000 and will be able to provide 1,000 gallons of water daily.
1000 gallons a day is already a pretty nice amount, but as you said, the maintenance work and costs are unknown.
Not revolutionary (Score:2, Insightful)
While this design is a step up, and it certainly must have been a great engineering challenge to build and integrate, there is no groundbreaking technology that goes into this. It's a simple reverse osmosis plant, based on technology that's already being used at commercial scale. The summary is also misleading - this system also requires a lot of energy, it just has a power source with it. In fact, it's almost certainly less efficient than a conventional RO system, both in terms of energy used and embedded
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That's what I was thinking - surely a hand pump would be much more useful most of the time? The solar panel would be good for keeping the unit busy when no one's around, but for a portable emergency supply you'd get more useful energy from people winding up a spring using a handle.
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Optional attachments... (Score:3, Insightful)
And for about 8 more dollars, they could attach a big funnel and bucket for those days when it rains and the solar part doesn't work so well.
Cost (Score:2)
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Desalination plants are being installed in several parts of Australia including a controversial one in Victoria. The funny bit is that our drought broke just as construction got under way.
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May seem funny but you know... will need it for the next one.
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Thats true.
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If you're in the middle of a drought, having a desalination plant is only useful if you're on the coast, the dry bits in the middle of Australia are quite a way from the sea.
Boats (Score:5, Insightful)
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Most commercial vessels (cruise ships, cargo/oil tankers, etc) already use evaporative systems (waste heat from engines/generators is used to flash heat water to steam, which is than condensed back into clean drinking water). A possible market would be smaller yachts and sail boats that sail around the Caribbean.
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Small reverse osmosis systems have been available for personal cruising boats for years. From units powered from the 12 volt battery system down to hand-pumped emergency units.
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For example a 45' viking that is running out of Jupiter is ideal of this. The one advantage of a solar cell approach is that if a boat has an outage (diesel goes out), then you still have water.
Try it (Score:1, Interesting)
See how long those panels remain attached once the "disadvantaged" figure out what they are worth.
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Probably not long.
But, let's see how long the limbs of the thief remain attached to his body once his disadvantaged neighbors find out that they are about to die because of dehydration.
Question (Score:5, Insightful)
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Re:Question (Score:4, Interesting)
* - I don't know if this is the correct term. The faster you turn the crank, a set of weighted brake shoes (or similar) move out towards a high friction surface. The faster you spin, the harder it becomes to continue. Or some such.
Re:Question (Score:4, Interesting)
Wikipedia claims that reverse osmosis requires 6kWh to produce 1000L of water, or 21.6 kJ/L.
To evaporate water already at 100C requires ~41kJ/mol, or 2.3kJ/L. To heat 1L of water from 20C to 100C requires 33.6kJ. So, by this very simplistic model it would require ~34kJ/L to desalinate water by boiling.
Now the efficiency of PV vs thermal in a solar powered system depends on the efficiencies of the collectors. PV is ~25%, at best, solar insolation -> electricity. Heating water to evaporate it is a much more difficult calculation. Basically water doesn't have to be at 100C to evaporate and the losses in a thermal system would increase as the temperature differential (system->ambient) increased but in the end I'm not really educated enough to comment accurately. Hopefully the numbers above will give you some feel for the problem though.
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The problem is that this temperature is too low to kill bacteria and other nasty stuff in the water. So you need to treat with UV and chemicals. This increases complexity of the system slightly
A shallow black pan and some clear plastic, (Score:2)
arched over it and you get purified, distilled H2O dripping own the clear plastic dome.
You don't need to hail this as revolutionary.
You can apply the principle to a pool, pond or lake full of water (better is its running water since oxygenation helps keep moss down.)
Paint the bottom or float a black pan below the surface and you can get solar evaporation.
The arched cover can be designed with ribs in it to carry the water down.
Solar Still FTW!!! (Score:2)
Man, that brought back memories!
I built my first solar still in 1966 with a black garbage bag, a washed 3lb. coffee can, 4 ft. of aquarium air tubing, two rocks, and an Army surplus entrenching tool, as a Cub Scout.
I'd guess that if I could do this from a rough sketch and a basic explanation of how it worked as an 8 year old kid, then a community with adults could also manage.
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Its a wonder people try to do anything any more - its already been done! How many of these will we need to get the flow rate they're talking about here?
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Brilliant!! And to think that nobody who ever was thirsty and living near the sea thought of that! Let's hope the rest of the world reads Slashdot, because there sure are some world-changing insights on it now and then.
Seriously: do the math. How many pans do you need to generate a liter per day? How much time does it take per pan to remove the salt, harvest the water, and insert new water? How much area does all this need?
MIT = big news (Score:2, Insightful)
The headline idea has a lots of flaws. For $8000 you can dig a well and install a pump that can supply the water for 250 people. Not only that, you'd have enough money left over to either cover any repair costs for a long time or to put towards another pump. A lot of African villages already have problems with more complex electric pumps, not being able to afford to pay for maintenance so the pumps sit inactive. T
Sigh... (Score:5, Informative)
Is reading that hard? DISASTER relief. You can't go around digging wells in a hurry. This system is designed to be put aboard an aircraft and flown to a disaster zone in a hurry to be used until normal operations can be resumed.
It is NOT a permanent solution.
Maybe if you could grasp this from the summary YOU could have gone to MIT and wouldn't be so upset.
What really is so hard to understand about the difference between disaster relief techonology and permanent solutions?
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This needs to be set up (need to find a good location, need to assemble it, can't start it working in the night), a steady supply of salt water is needed to feed into it, people need to be trained to clean or change the filters.
This isn't going to be a rapid response system either. A lot of the examples given in the article (desert farmland, Haiti 1 year on) are situations where a medium to long term solution is needed.
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Sure, wells are a more permanent solution, but can you airdrop a water well, and is it producing drinkable water on t
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Considering lots of wells are dug by people living in these nations, I'd imagine that if you offered someone $8K ($3K more than the typical cost) for a weeks work (depending on the depth and nature of the well), they'd bite your hand off.
There'd be plenty of money left to transport enough water to last people until the well was ready to use. Alternatively you could just drop a
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Innovation????? (Score:4, Insightful)
Sorry, but this just looks like a bog-standard boat desalinization system hooked up to some solar cells. I fail to see what is so earth-shattering about it.
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The trick for this application (and I don't know if MIT solved it or not) isn't the concept, which is obvious to almost anyone with an engineering or technical background. Rather, it's the implementation that will make it big. Anyone can hook up a desalinization system to solar cells; what you need to be able to do for this situation is make it cheap, light, mass-producible, rugged, reliable, and easy to operate and maintain.
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Actually the project is a testbed for some software algorithms for optimal control of systems in the context of variable power availability (as is the case with solar). Presumably this "smart" controller can achieve significantly higher throughput than a naive approach, for example it can probably optimize the process so that the power-consuming components are operating in their most efficient range over a wide range of input power availability.
The components of the device are all off the shelf items, the
Meanwhile, over in the real world.... (Score:2)
....The Third Worlders will quickly strip everything shiny off the systems and sell the metal to make a quick buck.
Not a prediction; reality. I've been there and seen it. Why do you think no-one really gives a damn about Haiti?
That's nice, but... (Score:2)
Longevity and Recreational Marine Use (Score:5, Informative)
The photo of the unit shows what appears to be a Clark Pump as used in Spectra Watermaker systems. (http://www.spectrawatermakers.com [spectrawatermakers.com]) These are popular in recreation long distance sailboats as they require less power for a given output than traditional RO systems.
As for reliability and longevity, much depends on the design. If you keep pressures reasonable, and flow excess raw water back to its source, the RO membranes will last many years and thousands of hours of use. The key is not running pressures so high that the membrane gets clogged with solids from the raw water. Pre filtering the raw water also is critical to not fouling the membranes. We run a 30 micron then 10 micron filter before out high pressure pump. The prefilters only need to be changed when fouled so their life span depends on the turbidity of the raw water.
We live aboard our boat and run a watermaker instead of using shoreside water sources. The unit is not as energy efficient as the MIT units. We have used it for years, have over 500 hours on it, and it has had near zero maintenance. In cold water, currently seawater is about 48F, we get 15gph, at 55F+ we get 18gph which is the max rated output, and above that we need to run at lower pressures to not saturate the membrane. We can get greater throughput by adding additional membranes. Adding a second membrane would double our output. (Sorry for the non metric units.) The Clark Pump system will get lower output, but the longevity of the membranes should be comparable. Membrane prices vary, but are typically in the US$250-US$500 range.
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Solar PV? (Score:2, Informative)
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,i>I see it depends on a continuos supply of sunlight; but what if it rains for days in a row?
I sincerely hope this was a joke or a troll. If the natives can't figure out how to get fresh water when it is raining, then we have a real problem.
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And I sincerely hope I figure out how to type tags correctly.